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Introduction The diagnosis of Type III sphincter of Oddi dysfunction (SOD), or functional biliary pain (FBP), remains controversial. The Rome IV classification discourages use of sphincter of Oddi (SO) manometry given its high risk profile and poor correlation between sphincter pressures and symptoms. Morphine augmented HIDA scanning (mHIDA) has been described as a non-invasive alternative to diagnose Type II SOD, though its role in the diagnosis of FBP is unclear. Although endoscopic biliary sphincterotomy (ES) is not a recommended therapy for FBP, intrasphincteric Botulinum toxin injection (Botox) to the SO seems to be of benefit to some patients. We aimed to evaluate the utility of mHIDA scanning in the assessment of FBP and establish whether there is an association between mHIDA scan results and response to Botox injection.Methods This was a retrospective review of patients with FBP who underwent endoscopic Botox injection to the SO between 2013 and 2019. Data were collected on demographics, mHIDA scan results, clinical response to Botox injection, use of opioids, and use of neuromodulatory agents. Continuous variables were reported as mean or median for normally distributed or skewed data respectively, and categorical variables were analysed using Fisher’s exact test. Logistic regression analysis was used to assess association between abnormal mHIDA scans and response to Botox injection to the SO. A biliary elimination fraction of ≤15% on mHIDA scanning was considered abnormal. A p value of <0.05 was considered statistically significant.Results Of 96 patients (89 female, mean age 42.7 years), 35 (36.5%) underwent mHIDA scanning as part of their diagnostic evaluation. Of these, 13 (37.1%) mHIDA scans were abnormal. There was no difference in response to Botox injection amongst those who had undergone mHIDA scanning compared to those that had not (p=0.245). An abnormal mHIDA was not associated with clinical response to Botox (Odds ratio (OR) 1.35 (0.39-4.66), p=0.631). Although patients with normal HIDA scans were more likely to have ongoing opioid use following Botox injection (OR 4.83 (1.10–21.28), p = 0.037), there was no association between abnormal mHIDA and age (OR 1.04 (0.96-1.13), p=0.33), gender (OR 1.2 (0.098-14.69), p=0.89), or use of neuromodulatory agents (0.34 (0.03-4.69), p=0.42).Conclusions This study suggests there is no role for mHIDA scanning in the evaluation of FBP. Scan performance and results correlate poorly with patient outcomes and response to treatment, emphasising FBP as a clinical diagnosis.